WO2010019563A1 - Synthèse de polymères arborescents par polymérisation raft (reversible addition-fragmentation chain transfer) contrôlée du type inimère - Google Patents

Synthèse de polymères arborescents par polymérisation raft (reversible addition-fragmentation chain transfer) contrôlée du type inimère Download PDF

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WO2010019563A1
WO2010019563A1 PCT/US2009/053395 US2009053395W WO2010019563A1 WO 2010019563 A1 WO2010019563 A1 WO 2010019563A1 US 2009053395 W US2009053395 W US 2009053395W WO 2010019563 A1 WO2010019563 A1 WO 2010019563A1
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polymer
monomer
styrene
group
dithioester
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Judit Eva Puskas
Andrew John Heidenreich
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The University Of Akron
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    • C08F12/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring
    • C08F12/02—Monomers containing only one unsaturated aliphatic radical
    • C08F12/04—Monomers containing only one unsaturated aliphatic radical containing one ring
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    • C08F12/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring
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    • C08F293/00—Macromolecular compounds obtained by polymerisation on to a macromolecule having groups capable of inducing the formation of new polymer chains bound exclusively at one or both ends of the starting macromolecule
    • C08F293/005—Macromolecular compounds obtained by polymerisation on to a macromolecule having groups capable of inducing the formation of new polymer chains bound exclusively at one or both ends of the starting macromolecule using free radical "living" or "controlled" polymerisation, e.g. using a complexing agent
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    • C08G83/00—Macromolecular compounds not provided for in groups C08G2/00 - C08G81/00
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    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L51/00—Compositions of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
    • C08L51/003—Compositions of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers grafted on to macromolecular compounds obtained by reactions only involving unsaturated carbon-to-carbon bonds
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    • C08L53/00—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
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    • C08L53/00—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
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    • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
    • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
    • C08F220/10—Esters
    • C08F220/12—Esters of monohydric alcohols or phenols
    • C08F220/16—Esters of monohydric alcohols or phenols of phenols or of alcohols containing two or more carbon atoms
    • C08F220/18—Esters of monohydric alcohols or phenols of phenols or of alcohols containing two or more carbon atoms with acrylic or methacrylic acids
    • C08F220/1804—C4-(meth)acrylate, e.g. butyl (meth)acrylate, isobutyl (meth)acrylate or tert-butyl (meth)acrylate
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    • C08F2438/00—Living radical polymerisation
    • C08F2438/03—Use of a di- or tri-thiocarbonylthio compound, e.g. di- or tri-thioester, di- or tri-thiocarbamate, or a xanthate as chain transfer agent, e.g . Reversible Addition Fragmentation chain Transfer [RAFT] or Macromolecular Design via Interchange of Xanthates [MADIX]

Definitions

  • the exemplary embodiment relates to free radical polymerization. It finds particular application in the synthesis of arborescent polymers and copolymers via RAFT polymerization and compositions comprising them. The polymer finds application in synthetic rubber compositions. However, it is to be appreciated that the present exemplary embodiment is also amendable to other like applications.
  • Arborescent (randomly branched) polymers have a cascade-type structure in which the polymer chains are branched. Such polymers have been synthesized using an anionic grafting method (See, for example, Gauthier, M., et al., Macromolecules, 24, 4548-4553, 1991).
  • This method involves the separate synthesis of narrow molecular weight distribution polymers by anionic polymerization, followed by several subsequent grafting reactions to yield higher degrees of branching.
  • the method does not lend itself to industrial processing due to stringent conditions and separate subsequent reaction steps used to build the arborescent polymer.
  • the resulting arborescent or polymers also have a narrow molecular weight distribution which does not necessarily yield optimum physical properties.
  • Arborescent polyisobutylene (arb-PIB) of high molecular weight has been synthesized by inimer (/n/tiator-monomer) -type living carbocationic polymerization of 4- (2-methoxyisopropyl) styrene and 4-(1 ,2-epoxisopropyl) styrene inimers. Subsequent development and study of these materials has resulted in the creation of arborescent block copolymer thermoplastic elastomers (TPEs) such as arb-PIB-b-PSt, arb-P ⁇ B-b- PpMeSt and others.
  • TPEs arborescent block copolymer thermoplastic elastomers
  • TPEs have shown to have a superior combination of properties compared to their linear tri-block counterparts. Additionally, these materials can be readily formed by one-pot synthesis.
  • Rizzardo, et al. report attempts to use vinylbenzyl dithiobenzoate (a mixture of meta and para isomers) in the synthesis of poly(methylmethacrylate-graft-styrene) (WO98/01478). The vinylbenzyl dithiobenzoate was co-polymerized with methylmethacrylate using azobisisobutyronitrile (AIBN) as the free-radical initiator at 60 0 C.
  • AIBN azobisisobutyronitrile
  • the resulting poly(vinylbenzyl dithiobenzoate-co-methylmethacrylate) was used as a chain transfer agent in mediating the bulk polymerization of styrene.
  • the authors report that the reaction resulted in a gel material.
  • RAFT Reversible addition-fragmentation chain transfer
  • CTA chain transfer agent
  • MWD narrow molecular weight distribution
  • CFRP chemical vapor deposition
  • This mechanism is applicable to a wide range of monomers, solvents, and temperatures.
  • Polymerizations have successfully been carried out in bulk, solution, emulsion or suspension to produce linear, graft, block, and star (co)polymers.
  • the dithioester chain transfer agent has a pungent odor, which makes it undesirable to work with, and the resulting polymers are colored due to the incorporation of the CTA.
  • a method of forming a randomly branched polymer includes polymerizing a monomer in the presence of a dithioester chain transfer agent having the general structure:
  • R is a free-radical forming leaving group that initiates free radical polymerization of the monomer and Z is a stabilizing group which stabilizes a radical formed from the dithioester, whereby fewer branches of the randomly branched polymer are formed through a dithioester radical than through the free radical formed from R.
  • Z may be selected from an aromatic hydrocarbon group and a heterocyclic group and their substituted derivatives, and combinations thereof.
  • R may be selected from the following optionally substituted groups: alkyl, a saturated, unsaturated, or aromatic carbocyclic or heterocyclic ring, an alkylthio, alkoxy, dialkylamino, an organometallic species, and a polymer chain prepared by any polymerization mechanism, and combinations thereof.
  • a randomly branched polymer includes at least one repeating monomer unit derived from an alpha-beta unsaturated monomer.
  • the polymer has a molecular weight distribution of at least 1.5.
  • the randomly branched polymer may have a weight average molecular weight of at least 0.5 kg/mole and in some embodiments, at least 3 kg/mole.
  • a randomly branched polymer is provided.
  • the randomly branched polymer is formed by a process which includes combining a monomer with a dithioester chain transfer agent.
  • the randomly branched polymer has a molecular weight of at least 0.5 kg/mole, and a molecular weight distribution of at least 1.5.
  • FIGURE 1 is an 1 H NMR spectra of an arborescent polymer (Sample ID 13) in accordance with the exemplary embodiment including a representative fragment of the expected branching point structure;
  • FIGURE 2 shows pseudo-first order kinetic rate plots for exemplary polymers in accordance with the exemplary embodiment over a time period of 1200 minutes;
  • FIGURE 3 is a plot of number-average molecular weight of exemplary polymers versus conversion on a scale of 0-1 , where 1 represents 100% conversion;
  • FIGURE 4 shows (SEC) Refractive Index Traces of a polymer in accordance with the exemplary embodiment for low and high conversion aliquots(A is for Example
  • FIGURE 5 shows (SEC) Rayleigh Ratio Traces of polymer in accordance with the exemplary embodiment for low and high conversion aliquots (A is for Example 2) (B is for Example 3);
  • FIGURES 6-9 show conformation plots of polymers in accordance with the exemplary embodiment in the log(molar mass) range of about 5.4-6.7;
  • FIGURE 10 shows overlaid SEC traces of the homopolymer of PfBA
  • FIGURE 11 shows an 1 H NMR spectrum of the ardP(tBA-d-S) formed in
  • FIGURE 13 shows the semilogarithmic rate plot for the polymerization in
  • FIGURE 14 shows the number-average molecular weight (M n ) versus fraction of converted monomer for Example 12;
  • FIGURE 15 shows overlaid SEC refractive index traces for arborescent polystyrene and arborescent poly(styrene-6-terf-butyl acrylate) (Example 16); and [0027] FIGURE 16 shows the 1 H NMR spectrum of arborescent poly(styrene-fe-terf- butyl acrylate) in CDCI 3 (Example 16).
  • the word polymer refers to homopolymers formed from a single monomer as well as copolymers formed from more than one monomer, block copolymers, and functionalized polymers.
  • the randomly branched polymers are formed by a reversible addition-fragmentation chain transfer (RAFT) polymerization of a monomer using a dithioester chain transfer agent (RAFT agent) and optionally an initiator.
  • RAFT reversible addition-fragmentation chain transfer
  • RAFT agent dithioester chain transfer agent
  • the randomly branched polymer can have high molecular weight and broad molecular weight distribution. It can, therefore, find particular ease of industrial processing in bulk. It may find particular application as an additive in rubber compositions and other like applications.
  • a polymerizable monomer can be any monomer capable of being polymerized, including dimers and oligomers of from about 2-5 repeat units and combinations thereof.
  • a "monomer unit” is an optionally repeating unit of a polymer which is derived from a monomer or chain transfer agent.
  • a "polymer,” as used herein, can be a homopolymer or copolymer, block copolymer, or functionalized polymer, and in the case of a copolymer may include monomer units from multiple monomers.
  • the resulting randomly branched polymer which is formed by the exemplary method described herein can comprise at least 50 monomer units, the majority of which may be derived from an alpha-beta unsaturated monomer, such as styrene.
  • the randomly branched polymers disclosed herein have several advantages.
  • the methodology is general forming a randomly branched styrene polymer combining a monomer with a dithioester chain transfer agent.
  • radicals are selected with similar reactivity in the system. This is achieved by careful selection of a combination of the RAFT agent, the monomer, and if necessary, the initiator. This allows for any undesirable smelling dithioester moiety from the chain transfer agent to form at the terminal ends of branches of the polymer rather than at a branching point making subsequent removal via cleavage possible.
  • Additional advantages are that the randomly branched polymers can be produced having high molecular weights and broad distributions in a one-pot synthesis. This makes for easier and less expensive bulk industrial processing.
  • a method of forming a randomly branched polymer includes combining a monomer with a dithioester chain transfer agent (CTA) (which may be referred to herein as an inimer) having the general structure represented by Structure 1 :
  • CTA dithioester chain transfer agent
  • the functional group R is a free-radical forming leaving group that initiates free radical polymerization of the monomer.
  • Z is a stabilizing group, different from R, which stabilizes a radical formed from the dithioester, whereby fewer branches of the randomly branched polymer are formed through a dithioester radical than through the free radical formed from R. In general, fewer than 1% of branches are formed via the dithioester radical.
  • the R group includes a polymerizable double bond which allows the R group to be incorporated into the polymer chain as a branch point.
  • the Z-group can be any conventional organic group, however, it is matched with the monomer to provide a stable dithioester radical, as described in greater detail below.
  • Scheme 1 illustrates the reversible fragmentation of the chain transfer agent: Scheme 1
  • the polymerizable R group is fragmented off to reinitiate polymerization during the RAFT process.
  • the Z-group stabilizes the intermediate radical, which is a determining factor in the rate of the polymerization.
  • P represents a radical formed from the monomer or polymerized monomer, optionally through the action of an initiator.
  • the R group may comprise a vinyl group and may have the general structure as shown in Structure 6. This structure contains a polymerizable double bond (e.g., a terminal vinyl group) so to incorporate into the polymer chain as a branch point:
  • Ri and R 2 are independently selected from the group consisting of hydrogen, alkyl, aryl, alkoxy, aryloxy, carboxy, acyloxy, aroyloxy, alkoxy-carbonyl, aryloxy- carbonyl, CO 2 H, CN, CONH 2 , halogen, and substituted derivatives thereof; and wherein
  • R — represents the location of the R — S bond in Structure 1.
  • Ri can be H
  • R 2 includes at least one carbon through which the R — S bond is formed.
  • Exemplary R groups include Structures 7, 8, 9, and 10:
  • Structure 7 Structure 8
  • Structure 9 Structure 10 where — represents the location of the R — S bond.
  • the selection of the Z-group may be dependent on the monomer to be polymerized, and may also be influenced by the selection of a solvent, if the polymerization is performed in a solvent.
  • the section of the Z group can be used to tune the reactivity depending on whether it is electron withdrawing or donating, or resonance stabilizing to give an optimum balance of radical stability and reactivity.
  • Exemplary Z groups include Structures 11 , 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 , 22, 23, 24, 25, 26, 27, 28 and 29:
  • n in structure 20 represents an integer and can be for example, from 1-10. and where
  • Structure 1 is a xanthate. xanthates are particularly useful chain transfer agents in the case of vinyl acetate polymerization.
  • the monomer to be polymerized can be any polymerizable monomer typically used in RAFT or other polymerizations. However, in the exemplary embodiment, the monomer and CTA and the initiator (if employed) are selected to be kinetically compatible. Additionally, in the case of a polymerization carried out in a solvent, the polymer formed from the monomer should be soluble in the solvent in order to achieve an optimum balance of radical stability and reactivity.
  • Exemplary polymerizable monomers include alpha-beta unsaturated aromatic and aliphatic monomers (monomers with a terminal vinyl group), such as styrene, p- chloro styrene, p-methyl styrene, p-bromo styrene, isoprene, butadiene, methyl methacryiate, N,N dimethyl acrylamide, acrylamide, hydroxyethyi methacrylate, acrylic acid, vinyl acetate, terf-butyl acrylate, n-butyl acrylate, methyl acrylate, methacrylonitrile, acrylonitrile, N-isopropyl acrylamide, dimethyl amino methacrylate N-vinylcarbazole, N- vinylpyrrolidone, vinylpyridine, vinylimidazole, vinyl chloride, and combinations thereof.
  • alpha-beta unsaturated aromatic and aliphatic monomers such as st
  • a single monomer is used.
  • the monomer may be styrene and the polymer formed is then a randomly branched polystyrene.
  • the CTA for styrene polymerization is 4-vinylbenzyl dithiobenozate.
  • the molar ratio of the monomer to CTA can be selected to achieve a polymer with a desired molecular weight.
  • the molar ratio of monomer (e.g., styrene) to the dithioester CTA is at least about 2:1 and can be up to about 1500:1.
  • the molar ratio of monomer to the CTA is at least about 50:1 or at least 200:1.
  • the ratio may be up to 1200:1 and in some embodiments can be about 500:1.
  • an initiator may be employed.
  • An exemplary initiator is one with a half-life (U 12 ) of about 10 hours, in particular, those which form radicals through photoexcitation or a redox reaction.
  • Exemplary initiators include: azobis(isobutyronitrile), 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2- methylpropanenitrile), 2,2'-azobis(2-methylbutanenitrile), 1 ,1'-azobis(1- cyclohexanenitrile), azo-f-butane, dicumyl hyponitrile, f-butyl peroxide, dilauroyl peroxide, succinic acid peroxide, dibenzoyl peroxide, di-f-butyl peroxyoxalate, 2,2'- azobis(2-methylbutanenitrile), azoisooctane, dibutyl hyponitrile, dicumyl hyponit
  • the polymerization can be performed in bulk, in solution (including aqueous or other solvents) in suspension or in emulsion to produce dendritic (co)polymers and block copolymers. Additionally, the exemplary materials allow for the ease and simplicity of one-pot synthesis.
  • Exemplary solvents which may be used in the case of solvent polymerization include toluene, benzene, tetrahyrofuran (THF), methyl ethyl ketone (MEK), or the like, in the case of water insoluble monomers, such as styrene.
  • water may be used as the solvent.
  • the reaction may be performed in the presence of an inert gas, such as nitrogen, argon, helium or the like, or other oxygen-free environment.
  • the reaction may be carried out at any temperature which is suitable to forming the free radicals and for ensuring progress of the polymerization.
  • a suitable temperature is in the range of 100- 120 0 C.
  • lower temperatures can be used, e.g., around 8O 0 C 1 and for ferf-butyl acrylate, around 60°c may be suitable.
  • Scheme 3 illustrates the polymerization of styrene when combined with the inimer (CTA) 4-vinylbenzyl dithiobenzoate, which may be performed in bulk. The result is a randomly branched polymer (polystyrene) with a higher molecular weight than can be achieved by conventional linear polymerization methods.
  • the inimer (Structure 2) having the benzyl radical and the vinyl group on the same fragment see Structure 5, Scheme 2) allow for the branching to form Structure 30:
  • the dithioester moieties can subsequently be removed to yield an exemplary randomly branched polymer of the present disclosure which is substantially free of dithioester groups.
  • the dithioester moieties are cleaved by adding a further charge of the monomer, e.g., styrene, or another reactive monomer, which may or may not be the same as is used in the primary reaction.
  • a further charge of the monomer e.g., styrene, or another reactive monomer, which may or may not be the same as is used in the primary reaction.
  • styrene is added, optionally, with an additional radical source, such as dicumyl peroxide. It is postulated that due the addition of dicumyl peroxide, high concentration of cumyl O radicals are generated, which preferentially react with the benzyl radicals that form via cleavage of the dithiobenzoate groups. This results in a permanently terminated polymer.
  • This method can be used for functionalizing any of the randomly branched polymers described herein. This can yield multifunctional polymers, advantageous for filler interaction and improving tire properties.
  • the cleaving may includes addition of a compound yielding a suitable functional group to form block copolymers and/or functionalized monomers.
  • the block copolymer product thus formed can have thermoplastic elastomeric properties and/or be amphiphilic.
  • the dithioester moieties may be cleaved by aminolysis, for example, by reacting the polymer with an amine.
  • the polymer may be quenched by cooling rapidly, e.g., with dry ice, either prior to or subsequent to cleaving the dithioester moieties.
  • the randomly branched polymer includes at least one repeating monomer unit wherein at least some of the branches are linked through a para-substituted vinyl benzyl unit as shown above in Structure 5.
  • the para-substituted vinyl benzyl-derived unit constitutes less than 5 mol% of the monomer units which make up the polymer.
  • the polymer may comprise at least 95 mol% of monomer-derived units and less than 1 mol% of dithioester moieties, and generally, all sulfur containing units total less than 0.1 mol% of the monomer units which make up the polymer. Based on the disappearance of the color during the cleaving, it appears that no dithioester remains in the polymer.
  • Molecular weight distribution is determined as the ratio of the weight average and number average molecular weights (M w /M n ) of the polymer formed. This is useful as a measure of the polydispersity of a polymer.
  • M w /M n is 1 for a perfectly monodisperse polymer.
  • the ratio is invariably >1 for actual polymers,
  • the molecular weight distribution M w /M n of the exemplary polymer is at least 1.4 or at least 1.5. In some embodiments, the M w /M n is at least 1.8 or at least 2.
  • the molecular weight M w of the polymer can be from about 0.5 kg/mole to about 1.0 x 10 4 kg/mole.
  • the number average molecular weight can be from about 0.5 kg/mole to about 1.0 x 10 4 kg/mole.
  • the average number of branches per chain can be at least 2, e.g., at least 3 and can b up to about 20, or higher.
  • branching analysis by NMR showed an average of 3.5 branches per chain for copolymerization of styrene and 4-vinylbenzyl dithiobenzoate in bulk conditions using thermal initiation at 110 0 C to give arborescent polystyrene (arbPSt).
  • branching of about 20 branches per chain was achieved.
  • a composition which incorporates the exemplary polymer contains at least 0.1% by weight of the polymer and an inorganic filler for rubber, such as carbon black, silica, alumina, aluminum hydroxide, zinc oxide, nanofillers and combinations thereof.
  • an inorganic filler for rubber such as carbon black, silica, alumina, aluminum hydroxide, zinc oxide, nanofillers and combinations thereof.
  • the composition is used to form at least a part of a tire.
  • the tire includes the exemplary polymer, in which case the polymer may comprise polyisoprene, polybutadiene, styrene-butadiene rubber (SBR) or combination thereof.
  • SBR styrene-butadiene rubber
  • rubber compositions used in tire components may be compounded by known methods, such as mixing one or more sulfur-vulcanizable constituent rubbers with various commonly used additive materials such as, for example, curing aids, such as sulfur, activators, retarders and accelerators, processing additives, such as oils, resins including tackifying resins, silicas, and plasticizers, fillers, pigments, fatty acid, zinc oxide, waxes, antioxidants, and antiozonants, peptizing agents, and reinforcing materials such as, for example, carbon black and silica.
  • the additives mentioned are selected and commonly used in conventional amounts.
  • the exemplary polymer may be incorporated along with the additives.
  • a biomedical device includes the exemplary polymer, in which case, it may comprise biocompatible monomers/polymer.
  • a randomly branched polymer is formed by a process which includes combining a monomer or a mixture of monomers with a dithioester chain transfer agent, wherein the polymer has a molecular weight of at least 0,5 kg/mole and a molecular weight distribution of at least 1.5.
  • the polymer may be formed by the above-described methods.
  • M n the theoretical number average molecular weight for a linear controlled/living polymerization of styrene in the presence of 4-vinylbenzyldithiobenzoate (VBThB) (a case in which VBThB acts only as a chain transfer agent and not a monomer), can be calculated as follows:
  • an arborescent polymer is formed by copolymerizing a first alpha-beta unsaturated aromatic or aliphatic monomer, such as styrene or te/t-butyl acrylate with a dithioester chain transfer agent as described herein, such as 4-vinylbenzyldithiobenzoate to form an arborescent polymer formed primarily of the polymerized monomer.
  • a second monomer may be added, which attaches to the terminal ends of the branches of the arborescent polymer.
  • the second monomer can be an alpha-beta unsaturated aromatic or aliphatic monomer, as described above.
  • 4-vinylbenzyldithiobenzoate may be copolymerized with te/t- butyl acrylate (first monomer) to form a branched poly(ferf-butyl acrylate) (PfBA), as described herein.
  • Post-polymerization hydrolysis e.g., with an organic acid, such as trifluoroacetic acid, may be performed to convert the hydrophobic arborescent poly(terf- butyl acrylate) to hydrophilic arborescent poly(acrylic acid).
  • the arborescent poly(acrylic acid) serves as a macroinimer which can be reacted with styrene (second monomer), e.g., in the presence of a free-radical initiator, such as azobisisobutyronitrile (AIBN) to form an arborescent block copolymer, arborescent poly(fe/t-butyl acrylate-styrene (arbP(tBA-b-S)).
  • a free-radical initiator such as azobisisobutyronitrile (AIBN)
  • AIBN azobisisobutyronitrile
  • the synthesis can be reversed, with styrene used as the first monomer.
  • BThB 4-vinylbenzyl dithiobenzoate
  • 4-vinylbenzyldithiobenzoate (Structure 2) was copolymerized with styrene by an inimer-type RAFT reaction, as follows. Styrene (327.9 g, 10.57 mol/L) and VBThB (1.74 g, 0.0215 mol/L) (Structure 2) were placed in a 500 ml. round bottomed flask equipped with a magnetic stirbar.
  • the reaction mixture was purged with dry nitrogen for 30 minutes before being immersed in a silicone oil bath at 110 0 C. Aliquots of approximately 5 ml. were taken periodically throughout the course of the polymerization and precipitated into methanol. The reaction was continued until the viscosity increased too high to allow removal of additional aliquots (19 hours 53 minutes). The reactions (aliquots) were quenched by exposure to air and cooling in dry ice. Once the reaction mixture was at room temperature, it was precipitated in methanol. The conversions of the aliquots (numbered Sample IDs 1-4) and final product (Sample ID 5, 32% conversion) were determined gravimetrically.
  • Table 1 summarizes the data for the sample aliquots, where M n and M w are the number and weight average MWs, R g , z and R h,2 are the z-average radii of gyration and hydrodynamic radii, and ⁇ w is the weight- average intrinsic viscosity, as measured by SEC. From the results, it can be concluded that high MW broad molecular weight distribution, branched (see conformation plots) polystyrene was formed. Table 1
  • Example 7 Low Molecular Weight Styrene Polymerization (Comparative Example)
  • CTA chain transfer agent
  • Figure 1 shows the 1 H NMR spectra for Sample 13 along with a representative fragment of the expected branching point structure.
  • the peaks at 7.08 and 6.60 are due to the resonance of the aromatic protons on both the styrene and VBThB.
  • Peaks A and B are both indicative of polystyrene.
  • Peak A represents both protons on the CH 2 in the polymer backbone, while B includes three peaks, one for each distinct methine triad on the polystyrene backbone.
  • the small, broad peak at 4.50 ppm (C) is assigned to the methine proton adjacent to the remaining dithioester moiety at the end of every branching point.
  • the 1 H NMR integrations show a 73:1 ratio of styrene to VBThB.
  • degree of polymerization n 245
  • branching density across the molecular weight there is a distribution of branching density across the molecular weight, with the higher molecular weight having more branches.
  • Figure 2 shows a pseudo-first order kinetic rate plot for in accordance with the exemplary embodiment for several examples over a time period of 1200 minutes.
  • Figure 3 is a plot of number-average molecular weight of the exemplary polymer versus conversion in the range of 0 to 33 %. Figures 2 and 3 suggest living conditions for Samples 1 and 13 but not for Sample 20.
  • Figure 4 shows (SEC) Refractive Index Traces of a polymer in accordance with the exemplary embodiment for low and high conversion aliquots.
  • Figure 5 shows (SEC) Rayleigh Ratio Traces of a polymer in accordance with the exemplary embodiment for low and high conversion aliquots.
  • the SEC refractive indexes shown in Figure 4 and the SEC Rayleigh ratios shown in Figure 5 traces were performed for the first and last aliquots of samples 1 , 5, 13, and 19.
  • the aliquots taken during the reaction displayed a broad, multimodal distribution.
  • the multimodal/broad distribution is known to lead to improved processability and combination of properties.
  • Equation 1 g', which represents the ratio of the Intrinsic Viscosity ( ⁇ w ) of the branched polymer to the linear polymer at the same molecular weight, was calculated from Equation 1 :
  • the g and h parameters are defined by the geometric and hydrodynamic dimensions, respectively, where the dimensions are compared to linear, monodisperse sample at the same weight-average molecular weight, p is a dimensionless parameter that is independent of bond angles and degree of polymerization, but remains a function of branching, polydispersity, and branch flexibility. (See Stockmayer, et al.) Table 6 summarizes the data.
  • a method of analyzing the conformation of a polymer chain is the conformational plot, which is a log-log plot of radius of gyration versus molar mass. It has been determined that for the SEC system used in these examples, conformation plots of linear polystyrenes fit the following Equation 6:
  • a conformation plot slope of less than 0.6477 for R 9 indicates a macromolecule that is in a more compact conformation, at a given molecular weight, than its linear counterpart.
  • a slope of 0.33 indicates a spherical conformation.
  • Figures 6- 9 show conformation plots of polymers in accordance with the exemplary embodiment in the log(molar mass) range of about 5.4-6.7. These plots show the conformation plots for the first and last aliquots for the exemplary arborescent polymers disclosed in Examples 2-6.
  • the slopes of the conformation plots of the example polymers range from 0.28-0.47, which are all below that of a linear polystyrene random coil.
  • VThB 4-vinylbenzyldithiobenzoate
  • VBThB 4-vinylbenzyldithiobenzoate
  • the reaction flask was purged with dry argon for 45 minutes before being immersed in a silicone oil bath at 60°C. Aliquots were taken periodically throughout the course of the polymerization and precipitated into 50/50 V/V mixture of methanol/water. The reaction was continued until the viscosity increased to a point at which it was too high to allow removal of additional aliquots (5 hours). The samples were later filtered and te/t-butyl acrylate was removed in the vacuum oven. The conversions of the aliquots (numbered Sample IDs 31-34) were determined gravimetrically. Table 8 summarizes the data for the sample aliquots. SEC traces of the polymer, performed as described above, obtained after 5 hrs.
  • Example 13 Hydrolysis of arborescent polv(ferf-butyl acrylate) to arborescent polv(acrylic acid)
  • ferf-butyl acrylate as a second monomer
  • AIBN 0.0027 mmol, 0.0005 g

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Abstract

Cette invention concerne des polymères ramifiés aléatoires, par exemple des homopolymères, des copolymères, des copolymères séquencés et des polymères fonctionnalisés qui peuvent être formés par polymérisation d’un monomère polymérisable, comme le styrène, avec un agent de transfert de chaîne dithioester qui comprend un groupe polymérisable. La réaction peut être effectuée dans une seule cuve. Le polymère ramifié aléatoire peut avoir un poids moléculaire élevé et une large répartition de poids moléculaires.
PCT/US2009/053395 2008-08-11 2009-08-11 Synthèse de polymères arborescents par polymérisation raft (reversible addition-fragmentation chain transfer) contrôlée du type inimère WO2010019563A1 (fr)

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CN103819390A (zh) * 2013-11-25 2014-05-28 南京工业大学 一种含末端羟基的raft链转移剂的合成方法
WO2018069678A1 (fr) * 2016-10-10 2018-04-19 Domino Uk Limited Copolymère séquencé ramifié

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CN112852091A (zh) * 2021-01-13 2021-05-28 邱元栏 一种可降解阻燃聚苯乙烯塑料及其制备方法
CN115819751B (zh) * 2022-12-08 2024-09-06 中国科学技术大学 支化大分子链转移剂及制备方法与应用

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TWI284783B (en) * 2003-05-08 2007-08-01 Du Pont Photoresist compositions and processes for preparing the same
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US20030050411A1 (en) * 2001-06-12 2003-03-13 Dow Global Technologies Inc. Use of polar monomers in olefin polymerization and polymers thereof
US20070299221A1 (en) * 2003-12-23 2007-12-27 Sebastien Perrier Polymerisation Using Chain Transfer Agents

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103819390A (zh) * 2013-11-25 2014-05-28 南京工业大学 一种含末端羟基的raft链转移剂的合成方法
WO2018069678A1 (fr) * 2016-10-10 2018-04-19 Domino Uk Limited Copolymère séquencé ramifié

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